He was the first Gaoranger to be chosen and worked a year alone with only Tetomu. He was in the Air Force. Tetomu recruited him during a flight mission, and he was considered missing in action by the Air Force. Because of this, he bleached his hair to become less recognizable. As a pilot, he is good at skydiving and English and his hobby is playing the ukulele. He was twenty-three when the Kakeru joined the team. At first, Gaku was quite humorless, he was upset that Kakeru has been chosen as leader instead of him. As time went on, Gaku opened up, and became especially close to Kakeru, often teasing him good naturally. Gaku is the one who insisted that the Gaorangers refer to each other by color and not use their personal names. They didn't formally introduce themselves until the battle was over. Being that his Power Animal is a bird, Gaku refused to eat bird meat (he seems to be the only one to have this tendency; neither Soutarou nor Kai have shown any problem eating cow meat and fish, respectively). When he fought his first org, the Scooter Org, it was too powerful so Tetomu had him seal it. It was released by Loki later and it upgraded to Bike Org. Gaku eventually defeated the Org. After the final battle, he returned his G-Phone and jacket to Tetomu and returned to the Air Force and his natural hair color.

Later in 'Hurricanger vs Gaoranger', he was kidnapped with his former team members by Tsuetsue and Yabaiba and their G-Phones were given to the Jakanja. He was impersonated by Satorakura of the Jakanja. They escaped with the help of the Hurricanger, Goraijer and Shurikenger and defeated Tsuetsue and Yabaiba and the Jakanja.